There are many systems for fabricating structural frameworks including the use of steel frameworks for industrial and residential buildings because they are comparatively inexpensive to build and can be assembled rapidly. These buildings, however, face a serious problem in their relatively low fire ratings since a fire can cause rapid expansion of steel columns and beams resulting in twisting and warping which may result in the necessity of complete replacement of the building.
Reinforced concrete offers substantial advantages over steel from the standpoint of fire rating and many specially designed concrete forms for such use have been proposed in the past. Some such forms are made of construction grade lumber and plywood which must be assembled into predetermined shapes for receiving poured concrete. Forms which are to be used multiple times may also be made from metals having the necessary rigidity and strength to support the weight of the fluid concrete during its pouring and initial stages of curing. These forms are made in many types and shapes and are provided with a variety of means for locking them in position for the pour and unlocking to facilitate their removal after the concrete is sufficiently hardened. Even with the use of forms, however, it is extremely difficult to place the reinforcing bar such that it will maintain a fixed relationship during the time the removable forms are being attached. Thus, there is a great deal of difficulty in the fabrication of such walls.
The present invention provides a new building system which combines the advantages of both reinforced concrete and steel frame structures in a very simple, efficient and economical manner. Specifically, the proposed building system utilizes outwardly projecting legs on a horizontally or vertically extending U-shaped member, known as a purlin, to connect with standard stirrups on conventional walls, coronas, columns or beams in a rebar assembly. In practice, the stirrups are force-fitted within the slot formed by the legs of the purlins extending outwardly from the surface of adjoining wall sections. In this manner, the rebar and the wall sections are connected in a uniframe construction without welding and a metal form can be fitted around the connection to form a channel into which fluid concrete may be poured.
The system may be used to connect precast concrete wall sections having purlins bolted or otherwise attached to the outer edges thereof with the slot of the U-shaped purlins extending outwardly from the surface of adjoining wall sections. The stirrups, generally rectangular in shape, hold the elongated reinforcing bars in spaced relationship and have an outside diameter that is substantially equal to the width of the outwardly facing slot in the purlin. Thus, each end of the stirrup members can be force-fit into the outwardly facing slot of a corresponding U-shaped purlin member of the adjacent wall panels to form a preliminary connection between the two panels. A removable form or plate may be attached on each side of a preliminary connection with the plates extending horizontally from concrete-panel-to-concrete-panel and vertically the length of the elongated reinforcing bars to form an enclosed channel such that a fluid concrete mixture poured into the enclosed channel fills the channel and joins the concrete panels in a permanent unitary structure.
In the preferred embodiment, at least one groove extends inwardly from the bottom wall of each U-shaped member to hold the end of the stirrup off the bottom wall such that poured fluid concrete can flow around a substantial portion of the stirrup member. Further, a plurality of orifices are formed in each side wall of each U-shaped member as well as in the bottom wall of the U-shaped member. Thus, poured fluid concrete can penetrate the plurality of side and bottom wall openings and provide continuous concrete inside and outside the U-shaped members to form a stronger joint. In addition, rebar protruding from the ends of prefabricated concrete wall sections can extend through the openings in the bottom wall into the center of the U-shaped members to be surrounded by poured concrete and provide a stronger connection between concrete panels. Also, a packing of gasket-seal material can be placed in the bottom of each rectangular spaced groove before the concrete wall panels are poured to form a moisture and vapor barrier between the U-shaped member and the concrete that extends the height of the concrete wall panels. In one version, the outer edges of the sides of the removable forms or plates are bent inwardly to contact the concrete panels and cause a space between the removable plate and the side walls of the U-shaped member so that poured concrete can penetrate the plurality of orifices in each side wall of the U-shaped member and provide continuous concrete inside and outside the U-shaped members. The plurality of openings formed in the bottom wall of each U-shaped member can also be used for receiving the ends of protruding reinforcing bars such that poured fluid concrete surrounds the ends of the protruding reinforcing bars to form a unitary structure.
The novel system also enables the formation of a unitary concrete structure without using preformed concrete wall panels.
Thus, it is one important object of the present invention to provide a simple and efficient manner of connecting preformed concrete panels to form a unitary wall section.
It is another important aspect of the present invention to provide a building system in which structural members can be easily formed with U-shaped purlins and elongated reinforcing bars.